Forms of uPA and α-granule proteins stored in day-13 QPD cultured megakaryocytes compared with platelets. Panels show proteins evaluated by Western blotting after SDS-PAGE. (A) Nonreduced (top panel) and reduced (bottom panel) uPA in QPD megakaryocytes (Q MK) compared with platelets (Q plt). Recombinant low-molecular-weight (LMW), single-chain (sc), and 2-chain (tc) uPA are shown for reference. High-molecular-weight complexes (* and **) and forms recognized by PAI-1 antibodies (*) are indicated. (B) TSP-1, VWF, and P-selectin in QPD megakaryocytes (Q MK), grown with (+) or without (−) plasma, compared with control (C plt) and QPD (Q plt) platelets.